(81c) Pyrolysis of Biomass Using FCC Catalyst

Rapid pyrolysis of biomass normally yields viscous, acidic, and unstable liquids in high yields if the pyrolysis is carried out using silica sand as the medium. Pyrolysis using ZSM5 catalysts yield a variety of products depending on the pyrolysis conditions. We investigated the pyrolysis of hybrid poplar wood using fluid catalytic cracking (FCC) catalysts in a bubbling fluidized bed pyrolysis reactor under similar conditions of temperature, pressure, and hourly space velocity as ZSM5 catalysts. The yield of pyrolysis liquids ranged from 30 wt% to 55 wt% depending on the catalyst and char yield ranged from 16 wt% to 20 wt%. Unlike the ZSM5 catalyst which showed extensive cracking of the carbohydrate decomposition products, the FCC catalyst showed only partial cracking of the carbohydrate decomposition products. In both cases, a large fraction of water was produced. The pyrolysis oils were characterized by 13C-nmr. FCC catalysts with high zeolite content (35 wt%) caused demethylation/demethoxylation of the lignin moieties and thus lowering the relative methoxyl content of the pyrolysis oils. However, FCC catalyst with low zeolite content had minimal effect on the relative methoxyl content of the pyrolysis oil. All catalysts types reduced the acetic acid content of the oils and the pH of the oils was about 3.4 compared to 2.6 for the pyrolysis oils produced using sand as the fluidizing medium. The viscosity of the catalytic pyrolysis oils were also lower than those produced without catalysts.